Portable radio devices are used in a wide variety of communication applications. A popular configuration of a portable radio device is as a two-way radio. Two-way radios operate using half duplex communication, where the device is either transmitting, receiving, or idle/monitoring one or more channels. Transmission is conventionally controlled using a “push to talk” button, referred to as PTT operation, but transmission can also be controlled by voice activity where, upon a user speaking, the radio device commences transmitting until the user stops speaking. Such voice activity detection (VAD) operation is especially desirable in applications where it may be inconvenient for the user to manually operate the radio, such as, for example, in the case of emergency personnel or in the case of covert applications.
Covert applications involve the user wearing the radio device in a manner that cannot be seen. As a result, the antenna used by the radio is in close proximity to the wearer's body which presents an issue with regard to specific absorption rate (SAR). SAR refers to the exposure of the body to electromagnetic radiation, which is typically a legally regulated parameter. In order to comply with SAR limits for covert applications the radiated power is typically cut back to meet the required SAR limit. Of course, it would be desirable to be able to transmit at full power.
Accordingly, there is a need for a method and apparatus for an antenna and arrangement that allows use of a covert radio device that allows full power transmission while meeting SAR limits.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.